Before the present invention, a commercially practical current limiting circuit breaker suitable for use in low voltage power distribution systems of about 600 volts or less had been sought by the power distribution and control industry for over 30 years. Various, sometimes conflicting requirements have to be met. For example, a commercially practical current limiting circuit breaker (a) must be repetitively operable at its maximum short circuit interrupting rating without repair of replacement of parts (This requirement precludes the use of fuses, fused switches, or fused circuit breakers for achieving current limiting.); (b) must not have a temperature rise at the terminals of more than 50.degree. Centigrade at rated steady state current to meet appropriate standards of safety and performance established for circuit breakers used in power distribution systems of 600 volts or less (This requirement precludes the use of a large built-in resistance to limit current.); (c) must have a design applicable to a wide range of steady state current ratings, from a few amperes to hundreds of amperes; (d) must have current limiting capabilities competitive with those of the best available other current limiting devices including fuses (This requires that the device will operate in a fraction of a millisecond when the available short circuit current is 100,000 amperes or more.); (e) must be compact enough to fit into existing circuit breaker panelboards (This requires that the ratio of interrupting rating to volume be equal to or greater than that for any prior circuit breaker.); (f) must use non-toxic, non-hazardous materials; (g) must have a response time which decreases proportionately as much as or faster than available short circuit current is increased; (h) must be economically competitive with present circuit protective devices; and (i) must function without inducing severe transient voltages. None of the prior current limiting circuit breakers meets all the above requirements.